1. Field of the Invention
The present invention relates to a method for detecting faults between storage devices, and a storage device used for the method.
2. Description of the Related Art
A data storage apparatus such as a disk array apparatus has a function of transferring data between storage devices. The storage devices are interconnected by using a communication line such as a Fibre Channel. If maintenance is carried out when faults occur in the communication line, checking must be executed as to recovery of the communication line. As a simple diagnosis technology to check on such recovery, for example, Japanese Patent Laid-open Publication No. 2000-315165 discloses a data acquisition and distribution device for running maintenance. In the data acquisition and distribution device, when a operational mode is switched from an on-line state to an off-line state, a test is conducted in which a set of identical test packets are sent/received between a communicating device through the communication line. That is, a time duration from transmission of test packets to the communicating device, to receiving a last returned test packet. If the time duration is within specified time, it is determined that the communicating device and the communication line are normal. On the other hand, if the time duration exceeds the specified time, it is determined that the communicating device and the communication line are faulty.
Such a maintenance test for operation is conducted to check on whether the devices of both sides and the communication line are normal or not.
The above-described maintenance test is a simple diagnosis for sending/receiving test packets between the data acquisition and distribution devices. Though it is only a light-load test for the data acquisition and distribution devices and the communication line, this test enables detection of permanent faults.
However, temporary faults or faults dependent on certain conditions may not be detected. For example, faults which occur in the case of heavy load operation such as copying of data between disk devices cannot be found. Thus, if a system is actually operated after completion of maintenance work or initial setting of a path, the same fault may be repeated, which necessitates the maintenance work to be carried out all over again.